1. Field of the Invention
The invention relates to a method of fabricating a sheet or a fabric with crystalline titanium dioxide (TiO2) nano-particles.
2. Description of Related Art
Crystalline titanium dioxide nano-particle is frequent used as a photocatalyst due to its superior oxidation-reduction ability and high chemical stability. Crystalline titanium dioxide nano-particle can be synthesized by various methods and one of methods is sol gel method. The usage of ionic liquid (IL) in sol gel method for synthesizing crystalline titanium dioxide nano-particle under ambient condition was first published in J. AM. CHEM. SOC. 2003, 125, 14960-14961, 2003. Owing to the self-organizing ability of ion liquid, anatase crystalline TiO2 nano-particle, which has large surface area, can be obtained by this method (“TiO2 particles” and “crystalline TiO2 nano-particles” both refer to the anatase crystalline TiO2 nano-particles thereinafter). Combining with the high microwave (MW) absorbing ability of ionic liquid, IL/MW method is recognized as a green synthetic method for synthesizing inorganic nano-material. The two principal benefits of this method are high reaction rate and short reaction time.
In photocatalytic water treatment application, crystalline TiO2 nano-particles, mainly anatase type, are directly dispersed in an aqueous phase or immobilized on different supports such as ceramic tile, glass, polymer material, stainless steel plate, aluminum sheets, and so on. In conventional immobilization process, because of high calcination temperature requirement of forming crystalline TiO2 nano-particles, above 400° C., high temperature-resistant materials, such as glass, steel, and the like, are generally used. However this is a costly process and thus the commercial application has met its bottleneck. Hence, the usage of low cost polymer material as the immobilization support is currently an active research topic in recent year.
Polymer material is thermal sensitive material. The immobilization of crystalline TiO2 nano-particles on the polymer material is generally by two step process. For example, TiO2 sol is firstly synthesized and then coated on the polymer materials by dip coating method. Alternatively, an embedding process can also be applied, where crystalline TiO2 nano-particles are embedded into melted polymer materials such as polyethylene by hot press at suitable condition. However, the crystalline TiO2 nano-particles are easily aggregated and difficult to be homogeneously dispersed in these methods and then the immobilization adhesion strength is poor and the crystalline TiO2 nano-particles peel off easily.